I'll try to explain. For starters I have to assume that the reader(s) of this blog are familiar with the general principles of quantum mechanics and the famous Schrodinger's Cat thought experiment.
There are a couple of leading interpretations to the often-cited result of the experiment, the cat being simultaneously alive and dead. One holds that the two stated exist "smeared" over one another until the box is opened, then reality "collapses" to one state or the other. The other interpretation - the Many Worlds version - has it that when the quantum event occurs that either kills the cat or does not kill it, two parallel universes are created: the cat is alive in one and dead in the other. When the observer opens the box, he finds out which universe he happens to be in.
OK - now, what if Many Worlds is true... and you're the cat? Two universes are created. You're alive in one and dead in the other. You cannot observe the fact that you're dead... so you must continue to exist in the universe where you're alive, and can observe the outcome!
Take this to the logical end... if every random chance is the result of a quantum event, and there are infinite universes that encompass all of these possibilities, you will continue to live in at least one of them as long as there exists a non-zero chance of you being alive.
What could be wrong with this? A few things. So don't try this at home. The Many Worlds interpretation could be wrong. If there's an afterlife then all bets are off- you would be able to observe a universe in which you had died.
But what if it's correct? It would explain a lot. We often hear that the odds of human life arising in the universe are infinitesimal. Well, this just happens to be one of the few universes where all those coincidences happened. Ever think that you were lucky to have survived something? Maybe in 99% of all possible universes, you didn't.
This raises a question in my mind(s): there have to be a lot of possible universes in which I could still exist. Why is my consciousness in this particular one? Is it,
- I have a consciousness in each universe, and they are not aware of each other or connected
- I exist and remember my life in the final universe in which I continue to exist
- I exist in the "best" of the possible universes - by some unknown measure of quality
No way to tell, of course, but intriguing. If all this is true, one must still be careful with one's safety. Perhaps even more so. We might have quantum immortality, but if we behave stupidly we limit ourselves to existing in a small number of possible universes, and many of them may not be pleasant.